Abstract: In air- and spacecraft and where drinking water supplies are scarce it is necessary to reuse the available water due to the limited tank volume available for the water supply. Such reuse calls for a water treatment. For this purpose a freeze concentration stage or preferably two such stages are integrated into a sequential waste water treatment system, including mechanical filters followed by the freeze concentration stage, which in turn is followed by micro- and ultrafiltration, reverse osmosis, and charcoal filter stages. A final stage includes a disinfection by ultraviolet radiation. The operation of the system is monitored by measuring the electrical conductivity of the water being treated. The use of one or two freeze concentration stages provides a universal cleaning capable of handling waste water of any composition. The selection of stages downstream of the freeze concentration stages is variable, depending on the degree of purification required.